1. Field of the Invention
The present invention relates to a novel lens driving mechanism and a novel image pickup device. More specifically, the present invention relates to a technology which makes it possible to achieve size reduction, in particular, size reduction of a lens barrel in a diametrical direction thereof.
2. Description of the Related Art
Recently, there is a demand for, along with automating a focusing operation and exposure determination, automatically overcoming image blurring caused by a movement of a camera occurring when pushing a shutter button, that is, shooting an image that one wants to shoot so that it is sharp without requiring any skill in correcting the camera movement.
There are broadly two methods of correcting camera movement: an electronic method and an optical method. The optical method is carried out by detecting any camera movement perpendicular to an optical axis with a sensor and shifting a correcting lens perpendicularly to the optical axis so as to correct the amount of movement.
Many related optical camera movement correcting mechanisms using a moving coil for moving a correcting lens have been proposed. A lens driving mechanism in such camera movement correcting mechanisms is disclosed in Japanese Unexamined Patent Application Publication No. 7-98470.
The lens driving mechanism disclosed in the aforementioned document is schematically illustrated in FIG. 14 and described.
A correcting lens 71 is supported by a supporting frame 72. The supporting frame 72 is supported by a support shaft 74y, secured to a supporting arm 75, so as to be slidable in a Y direction perpendicular to an optical axis of the correcting lens 71. The supporting arm 75 is supported by a support shaft 74p, secured to a lens barrel 710, so as to be slidable in an X direction perpendicular to the optical axis of the correcting lens 71 and the Y direction. Therefore, the supporting frame 72 supporting the correcting lens 71 is movable along with the supporting arm 75 in the X direction with respect to the lens;,barrel 710, and in the Y direction with respect to the lens barrel 710 and the supporting arm 75.
Two coils, that is, a Y-direction driving coil 79y and an X-direction driving coil 79p are supported by the supporting frame 72. Magnets and yokes (not shown) for the respective coils 79y and 79p are disposed at the lens barrel 710.
When the coil 79y is energized, a thrust is generated in a Y direction in the coil 79y, causing the supporting frame 72 to move in the Y direction with respect to the lens barrel 710 and the supporting shaft 75. When the coil 79b is energized, a thrust is generated in an X direction in the coil 79p, causing the supporting frame 72 to move, along with the supporting arm 75, in the X direction with respect to the lens barrel 710.
By virtue of the above-described structure, the supporting shaft 72, that is, the lens 71 can move in all directions perpendicular to the optical axis thereof.
In the lens driving mechanism disclosed in the aforementioned document and shown in FIG. 14, since a structure in which the direction of movement of movable members (the supporting frame 72 and the supporting arm 75) is guided by guide shafts (the supporting shafts 74y and 74p) is used, two movable members (the supporting frame 72 and the supporting arm 75) are required for shifting the correcting lens 71 in all directions perpendicular to the optical axis thereof. This means that the structure includes two movable members that are disposed above and below each other vertically. Therefore, the structure inevitably becomes sophisticated and large.
To overcome this problem, a lens driving mechanism (shown in FIG. 15) using only one movable member by opposing the movable member with respect to a stationary member, such as a housing, via small balls has been proposed.
In the lens driving mechanism shown in FIG. 15, with three small balls d, d, and d being interposed between a movable frame b holding a correcting lens a and a stationary frame c secured to a lens barrel (not shown), a coil spring g is compressed between the movable frame b and a spring holding frame f held by the stationary frame c with screws e and e, and the movable frame b is biased towards the stationary frame c via the small balls d, d, and d by the resiliency of the coil spring g. This allows the movable frame b to move in an X direction or a Y direction by the resiliency of the coil spring g and the opposing force resulting from contact of the movable frame b with the small balls d, d, and d while the movable frame b is being held in the optical axis direction.
Two coils hx and hy are held by the movable frame b, and magnets jx and jy are held by the stationary frame c so that the respective coils hx and hy are disposed between the stationary frame c and a yoke i. Energizing the coil hx generates a thrust in an X axis direction in the coil hx, causing the movable frame b holding the coil hx and thus the correcting lens a to move in the X axis direction. Energizing the coil hy causes a thrust to be generated in a Y axis direction in the coil hy, causing the movable frame b holding the coil hy and thus the correcting lens a to move in the Y axis direction. Therefore, energizing the coils hx and hy as required causes the movable frame b and thus the correcting lens a to move in the X-axis direction and the Y-axis direction.
The lens driving mechanism shown in FIG. 15 only needs one movable member, so that the structure of the lens driving mechanism is simplified, and its size is reduced.